FBN3 encodes fibrillin-3, a structural glycoprotein that assembles into 10-12 nm extracellular microfibrils, which provide force-bearing structural support and elasticity to connective tissues 1. Like other fibrillins, FBN3 contains calcium-binding epidermal growth factor domains and likely contributes to transforming growth factor-β (TGF-β) bioavailability regulation through interactions with latent TGF-β binding proteins 1. FBN3 is expressed early in human development, particularly in embryonic and fetal tissues 1. Unlike FBN1 and FBN2, which cause well-characterized fibrillinopathies (Marfan syndrome and congenital contractural arachnodactyly, respectively), FBN3 is degenerate and nonfunctional in rodent models, complicating disease investigation 2. Recent evidence associates FBN3 mutations with Bardet-Biedl syndrome (BBS), a ciliopathy characterized by developmental delay, cognitive impairment, obesity, and skeletal anomalies 34. Additionally, rare FBN3 variants have been identified in polycystic ovary syndrome (PCOS) patients, though FBN3 expression in ovarian tissue is substantially lower than FBN1 56. FBN3 polymorphisms may also influence autoimmune thyroid disease risk through TGF-β regulation 7. These findings expand fibrillin disease pathways beyond classical connective tissue disorders.